PLATO and Pythagoras say that motion is a change and
alteration in matter. Aristotle, that it is the actual operation of that which may be moved. Democritus, that there
is but one sort of motion, and it is that which is vibratory.
Epicurus, that there are two species of motion, one perpendicular, and the other oblique. Herophilus, that one
species of motion is obvious only to reason, the other to
sense. Heraclitus utterly denies that there is any thing of
quiet or repose in nature; for that is the state of the dead;
one sort of motion is eternal, which he assigns to beings
eternal, the other perishable, to those things which are perishable.